Many commercial products are made from styrene and other polymerized vinyl aromatic monomers. Vinyl aromatic monomers, such as styrene, may autopolymerize, which can be undesirable when operating a monomer production unit. In a typical styrene production unit, a distillation is performed to separate styrene from other compounds, such as ethyl benzene. When polymerization of styrene occurs while operating a styrene production unit, styrene product may be lost and/or the styrene production unit may become inoperable, typically due to plugging caused by polystyrene.
Due, at least in part, to the fact that the autopolymerization of styrene is accelerated by heat, the distillation of styrene and other vinyl aromatic monomers usually is performed at reduced temperatures and low pressures (vacuum), typically at a pressure and temperature that is as low as possible.
In addition to these distillation parameters, 4-tert-butylcatechol (TBC) has been added to product styrene to prevent or minimize polymerization during transport of the product styrene to a polystyrene production unit. Some of the TBC added to the styrene product can be recycled to the styrene product distillation column through the reflux, but this TBC is usually ineffective due a lack of oxygen in the low pressure (vacuum) distillation columns. As a result, TBC typically exits with the tars stream and is burned as waste.
Methods of inhibiting polymerization of styrene and other vinyl aromatic monomers that reduce the amount of TBC used as an inhibitor and/or increase the effectiveness of TBC as an inhibitor, especially in a distillation column, are desired.